Agar: A Versatile Biopolymer with Diverse Applications

What Is Agar?

Agar is a natural polysaccharide extracted from red algae, primarily species of the genera Gelidium and Gracilaria. Agar is composed of two primary components: agarose and agaropectin. It is widely used in the food industry, pharmaceutical industry, bioengineering and other fields. It has coagulation and stability and is often used as a thickener, coagulant, suspending agent, emulsifier, stabilizer and preservative.

Physical and Chemical Properties of Agar

• Solubility

At room temperature, agar is neither soluble in water nor in inorganic and organic solvents. It is only slightly soluble in ethanolamine and formamide, but it can be dissolved in water and some solvents under heating conditions.

Dried agar can absorb water and swell at room temperature, and the water absorption rate can reach 20 times. It can be dissolved in water to form a solution when heated to 95℃. Agar solution can form gel at room temperature. Compared with other substances that can form gel, it has the strongest gel ability at the same concentration. Even a 0.1% agar solution can solidify at around 30℃.

Agar can also be dissolved in boiling low-concentration ethanol (30% - 50%) solutions. In some high-concentration electrolyte solutions, such as sodium sulfate, magnesium sulfate or ammonium sulfate, it will be salted out and precipitated.

• Flocculation

Adding 10 times the volume of ethanol, isopropanol or acetone to the agar solution can cause agar to flocculate and precipitate from the aqueous solution. As well, a salt solution of calcium sulphate, magnesium sulphate or ammonium sulphate solutions will salt out agar solutions. Thanks to this property, you can dehydrate agar gel during the agar extraction.

• Gel Temperature Hysteresis

Agar gel is a gel that can be reversed in temperature. The gel will melt when hot and harden again when chilled and allowed to stand (which can be repeated again). The solidification point of agar solution is between 32°C and 43°C and the melting point of agar gel is between 75°C and 90°C.

The melting point is very high as compared to the solidification point, which is peculiar to agar. It is called "hysteresis phenomenon". The high hysteresis of agar explains many of its use advantages.

• Viscosity

The viscosity of agar aqueous solution (sol) varies depending on the type of raw materials, the quality of raw materials, the conditions of extraction, the pH of the solution, the amount of inorganic salts, the concentration of agar during measurement, the temperature and the addition of electrolytes.

In the extraction process of industrial agar, due to the treatment of chemical reagents, it has been damaged to a certain extent, and its viscosity is low. In addition, the viscosity of agar will decrease significantly after the agar solution is treated with high temperature, electrolytes, inorganic acids or acidic salts.

• Non-Acidic Degradation

A large number of viscosity, diffraction and gel strength experiments and studies have shown that pure dry agar is extremely stable and difficult to degrade at room temperature. However, if it contains impurities, is at high temperature, is affected by ultrasound, strong gamma rays, strong stirring and other factors, it will cause the agar molecular chain to break and degrade, making some physical and chemical properties of agar worse.

• Gelation

The biggest feature of agar is that it has gel properties. Even a 0.004% agar solution can form a gel at room temperature. Compared with other substances that can form a gel, its gel strength is the highest at the same concentration. When agar forms a gel, no coagulant is required.

• Clarity and Inertness

Agar gel is highly transparent, and biological samples and chemical reactions can be easily observed. In addition, thanks to its chemical inertness, it is compatible with a variety of substances and organisms.

Agar from Alfa Chemistry

Catalog	Product Name
ACM9002180-33	Select agar
ACM9002180-32	Purified agar, BioReagent,gel strength(400 g/cm2)
ACM9002180-31	Noble agar
ACM9002180-30	Agar, Type M, suitable for plant cell culture
ACM9002180-29	Agar, Type E, suitable for plant cell culture
ACM9002180-28	Agar, Type A, suitable for plant cell culture
ACM9002180-27	Agar, Type A, Ash : 5-6%
ACM9002180-26	Agar, Suitable for plant cell culture, powder
ACM9002180-25	Agar, Suitable for microbiology, loss : ≤12 % loss on drying, quality level : 100
ACM9002180-24	Agar, Suitable for microbiology, loss : ≤10 % loss on drying, quality level : 200
ACM9002180-23	Agar, Suitable for microbiology, loss : ≤10 % loss on drying, quality level : 100
ACM9002180-22	Agar, Puriy ≥ 95%
ACM9002180-21	Agar, Powder,suitable for plant cell culture
ACM9002180-20	Agar, Powder, suitable for microbiology
ACM9002180-19	Agar, Plant cell culture tested
ACM9002180-18	Agar, Pharmaceutical grade
ACM9002180-17	Agar, High purity, low ionic content, low gel strenght
ACM9002180-16	Agar, High gel strength, suitable for plant cell culture
ACM9002180-15	Agar, Granulated, purified and free from inhibitors, suitable for microbiology
ACM9002180-14	Agar, For molecular biology
ACM9002180-13	Agar, For membrane filtration, low gel strengh
ACM9002180-12	Agar, For chromogenic media
ACM9002180-11	Agar, Food grade
ACM9002180-10	Agar, BioReagent, gel strength(1200 g/cm2)
ACM9002180-9	Agar, BioReagent
ACM9002180-8	Agar, Bacteriological, microbiology tested, suitable for plant cell culture, granular
ACM9002180-7	Agar, Bacteriological grade
ACM9002180-6	Agar, Ash ≤ 5.0%, Lowgelstrength(700-900 g/cm2)
ACM9002180-5	Agar, Ash ≤ 5.0%, High gel strength(1400 g/cm2)
ACM9002180-4	Agar, Ash ≤ 5.0%, High gel strength(1000-1200 g/cm2)
ACM9002180-3	Agar, Ash ≤ 1.5%, Low gel strength(700-900 g/cm2)
ACM9002180-2	Agar, Ash ≤ 1.5%, High gel strength(1000-1200 g/cm2)
ACM9002180-1	Agar, Ash : 2.0-4.5%

Applications of Agar

• Microbiology

• Culture Media: Agar is a common culture media that is used to grow microbes. The gelling nature of the material creates a hard surface for bacterial and fungal colonies to grow on.
• Electrophoresis: Agarose gels are used in electrophoresis techniques (gel electrophoresis and pulsed field gel electrophoresis) to fragment DNA and RNA by size.

• Food Industry

• Thickener and Gelling Agent: Agar is used as a natural thickener and gelling agent in jellies, puddings, desserts etc. It is a favourite for vegans and vegetarians to replace gelatin.
• Clearing Agent: Agar is useful to make wine, fruit juice and so on clear by removing suspended solids.

• Pharmaceutical Industry

• Drug Delivery: Agar-based hydrogels in drug delivery to regulate the release of medication.
• Wound Dressing: Agar dressings are used in the wound healing because they are absorbent and emollient.

• Biotechnology

• Tissue Engineering: Agar is an encapsulant material for tissue engineering which is applied to support the growth and differentiation of cells.
• Immunodiffusion: Antigen and antibody detection using agar gel diffusion.

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